The real scandal: science denialism at Susan G. Komen for the Cure®

Double X Science is pleased to be able to repost, with permission, this important piece courtesy of author Christie Aschwanden and the Last Word on Nothing website, focused on the things that science teaches us we still don’t know…but want to find out. 
You’ll notice that the focus of this article is the way that the Komen foundation blames the individual with the disease for having it, relying on what Aschwanden aptly calls “breast cancer’s false narrative.” This “blame the person” tactic seems to be especially common in women’s health, with an emphasis on the way a woman allegedly does the wrong thing or thinks the wrong thoughts or doesn’t work hard enough willing herself well, making her disease her fault, instead of the fault of nature, mutations, cell division gone astray, and the countless other molecular factors that accumulate into what we call “disease.” In the case of breast cancer, it’s not one monolith of disease that the decision to screen will magically stop.
Many thanks to Christie Aschwanden and the Last Word on Nothing for graciously agreeing to this important repost. –The DXS Editors ——————————————–
Is breast cancer threatening your life? This Susan G. Komen for the Cure® ad leaves no doubt about who’s to blame —you are.
Over the last week or so, critics have found many reasons to fault Susan G. Komen for the Cure®. The scrutiny began with the revelation that the group was halting its grants to Planned Parenthood.  The decision seemed like a punitive act that would harm low-income women (the money had funded health services like clinical breast exams), and Komen’s public entry into the culture wars came as a shock to supporters who’d viewed the group as nonpartisan.* Chatter on the intertubes quickly blamed the move on Komen’s new Vice-President of Public Policy, Karen Handel, a failed GOP candidate who ran for governor in Georgia on a platform that called for defunding Planned Parenthood.** Komen’s founder, Ambassador Nancy Brinker, awkwardly attempted to explain the decision, and yesterday, Handel resigned her position. (Whether she’ll receive a golden parachute remains unclear, but former CEO Hala Moddelmog received $277,864 in 2010, despite her resignation at the end of 2009.)
The Planned Parenthood debacle brought renewed attention to other controversies that have hounded Komen in recent years—like its “lawsuits for the cure” program that spent nearly $1 million suing groups like “cupcakes for the cure” and “kites for the cure” over their daring attempts to use the now-trademarked phrase “for the cure.” Critics also pointed to Komen’s relentless marketing of pink ribbon-themed products, including a Komen-branded perfume alleged to contain carcinogens, and pink buckets of fried chicken, a campaign that led one rival breast cancer advocacy group to ask, “what the cluck?”
But these problems are minuscule compared to Komen’s biggest failing—its near outright denial of tumor biology. The pink arrow ads they ran in magazines a few months back provide a prime example. “What’s key to surviving breast cancer? YOU. Get screened now,” the ad says. The unmistakeable takeaway? It’s your fault if you die of cancer. The blurb below the big arrow explains why. “Early detection saves lives. The 5-year survival rate for breast cancer when caught early is 98%. When it’s not? 23%.”
If only it were that simple. As I’ve written previously here, the notion that breast cancer is a uniformly progressive disease that starts small and only grows and spreads if you don’t stop it in time is flat out wrong. I call it breast cancer’s false narrative, and it’s a fairy tale that Komen has relentlessly perpetuated.
It was a mistake that most everyone made in the early days. When mammography was new and breast cancer had not yet become a discussion for the dinner table, it really did seem like all it would take to stop breast cancer was awareness and vigilant screening. The thing about the false narrative is that it makes intuitive sense–a tumor starts as one rogue cell that grows out of control, eventually becoming a palpable tumor that gets bigger and bigger until it escapes its local environment and becomes metastatic, the deadly trait that’s necessary to kill you. And this story has a grain of truth to it—it’s just that it’s far more complicated than that.
Years of research have led scientists to discover that breast tumors are not all alike. Some are fast moving and aggressive, others are never fated to metastasize. The problem is that right now we don’t have a surefire way to predict in advance whether a cancer will spread or how aggressive it might become. (Scientists are working on the problem though.)
Some breast cancers will never become invasive and don’t need treatment. These are the ones most apt to be found on a screening mammogram, and they’re the ones that make people such devoted advocates of mammography.H. Gilbert Welch of the Dartmouth Institute for Health Policy and Clinical Practice, calls this the overdiagnosis paradox. Overdiagnosis is what happens when a mammogram finds an indolent cancer. A healthy person whose life was never threatened by breast cancer is suddenly turned into a cancer survivor. She thinks the mammogram saved her life, and so she becomes an advocate of the test.
Some cancers behave just the opposite of these slow-growing, indolent ones. Researchers now know that some cancers are extremely aggressive from the start. There’s simply no such thing as “early” detection for these cancers. By the time they’re detectable by any of our existing methods, they’ve already metastasized. These are the really awful, most deadly cancers, and screening mammograms*** will not stop them.
Then there are cancers that fall somewhere in between the two extremes. These are the ones most likely to be helped by screening mammography, and they’re the lives that mammography saves. How many? For women age 50 to 70, routine screening mammography decreases mortality by 15 to 20% (numbers are lower for younger women). One thousand women in their 50′s have to be screened for 10 years for a single life to be saved.
So let’s recap. Getting “screened now,” as the Komen ad instructs can lead to three possible outcomes. One, it finds a cancer than never needed finding. You go from being a healthy person to a cancer survivor, and if you got the mammogram because of Komen’s prodding, you probably become a Komen supporter. Perhaps a staunch one, because hey—they saved your life and now you have a happy story to share with other supporters. Another possibility is that the mammogram finds a cancer that’s the really bad kind, but you die anyway. You probably don’t die later than you would have without the mammogram, but it might look that way because of a problem called “lead time bias.” The third possibility is that you find a cancer that’s amenable to treatment and instead of dying like you would without treatment, your life is saved. Here again, you’re grateful to Komen, and in this case, your life truly was saved.
Right now, breast cancer screening sucks. It’s not very effective, and if you measure it solely based on the number of lives saved versus healthy people unnecessarily subjected to cancer treatments, it seems to cause more harm than good. For every life saved, about 10 more lives are unnecessarily turned upside down by a cancer diagnosis that will only harm them. In a study published online in November, Danish researchers concluded that, “Avoiding getting screening mammograms reduces the risk of becoming a breast cancer patient by one-third.”
But it’s not quite that simple. Some people really are helped by mammography screening, and if you’re the one helped, it’s hard to discount that one life. Right now mammography is the best tool we have. Welch, who has spent more time than probably anyone else in America studying this issue, has deemed the decision about whether or not to get breast cancer screening a “close call.”
Reasonable women can decide that for them, the potential benefits outweigh the risks. Other reasonable women will decide that for them, the risks outweigh the potential benefits.
Komen isn’t wrong to encourage women to consider mammography. But they’re dead wrong to imply that “the key to surviving breast cancer” is “you” and the difference between a 98% survival rate and a 23% one is vigilance on the part of the victim. This message flies in the face of basic cancer biology.
Between 2004 to 2009, Komen allocated 47% of it $1.54 billion toward education and screening.  Much of its education messaging promotes the same false narrative as its ads, which means they are not only not furthering the search for a cure, they are harming the cause. By implying that the solution to breast cancer is screening, Komen distracts attention from the real problem, which is that way too many women (and men) are still dying of breast cancer, and screening is not saving them. We still can’t prevent breast cancer, because we don’t know what causes it.
To explain why Komen’s fixation on an unscientific story matters, I want to introduce you to Rachel Cheetham Moro. Moro was a cancer blogger, but she won’t be weighing in on this latest Komen controversy, because she died Monday of metastatic breast cancer. Before she left us, she had plenty to say about the false narrative Komen was peddling. Last October she wrote,
How dare Komen so FALSELY suggest that a screening mammogram is all it takes to avoid metastatic breast cancer? How dare Komen so CRUELLY suggest that “not getting screened for breast cancer in time” would be THE reason and the FAULT of the person with metastatic disease who misses out on all the experiences and joyous events of a long and healthy life that so many others take for granted? How dare you, Komen? How dare you? Continue reading

Biology Explainer: The big 4 building blocks of life–carbohydrates, fats, proteins, and nucleic acids

The short version
  • The four basic categories of molecules for building life are carbohydrates, lipids, proteins, and nucleic acids.
  • Carbohydrates serve many purposes, from energy to structure to chemical communication, as monomers or polymers.
  • Lipids, which are hydrophobic, also have different purposes, including energy storage, structure, and signaling.
  • Proteins, made of amino acids in up to four structural levels, are involved in just about every process of life.                                                                                                      
  • The nucleic acids DNA and RNA consist of four nucleotide building blocks, and each has different purposes.
The longer version
Life is so diverse and unwieldy, it may surprise you to learn that we can break it down into four basic categories of molecules. Possibly even more implausible is the fact that two of these categories of large molecules themselves break down into a surprisingly small number of building blocks. The proteins that make up all of the living things on this planet and ensure their appropriate structure and smooth function consist of only 20 different kinds of building blocks. Nucleic acids, specifically DNA, are even more basic: only four different kinds of molecules provide the materials to build the countless different genetic codes that translate into all the different walking, swimming, crawling, oozing, and/or photosynthesizing organisms that populate the third rock from the Sun.

                                                  

Big Molecules with Small Building Blocks

The functional groups, assembled into building blocks on backbones of carbon atoms, can be bonded together to yield large molecules that we classify into four basic categories. These molecules, in many different permutations, are the basis for the diversity that we see among living things. They can consist of thousands of atoms, but only a handful of different kinds of atoms form them. It’s like building apartment buildings using a small selection of different materials: bricks, mortar, iron, glass, and wood. Arranged in different ways, these few materials can yield a huge variety of structures.

We encountered functional groups and the SPHONC in Chapter 3. These components form the four categories of molecules of life. These Big Four biological molecules are carbohydrates, lipids, proteins, and nucleic acids. They can have many roles, from giving an organism structure to being involved in one of the millions of processes of living. Let’s meet each category individually and discover the basic roles of each in the structure and function of life.
Carbohydrates

You have met carbohydrates before, whether you know it or not. We refer to them casually as “sugars,” molecules made of carbon, hydrogen, and oxygen. A sugar molecule has a carbon backbone, usually five or six carbons in the ones we’ll discuss here, but it can be as few as three. Sugar molecules can link together in pairs or in chains or branching “trees,” either for structure or energy storage.

When you look on a nutrition label, you’ll see reference to “sugars.” That term includes carbohydrates that provide energy, which we get from breaking the chemical bonds in a sugar called glucose. The “sugars” on a nutrition label also include those that give structure to a plant, which we call fiber. Both are important nutrients for people.

Sugars serve many purposes. They give crunch to the cell walls of a plant or the exoskeleton of a beetle and chemical energy to the marathon runner. When attached to other molecules, like proteins or fats, they aid in communication between cells. But before we get any further into their uses, let’s talk structure.

The sugars we encounter most in basic biology have their five or six carbons linked together in a ring. There’s no need to dive deep into organic chemistry, but there are a couple of essential things to know to interpret the standard representations of these molecules.

Check out the sugars depicted in the figure. The top-left molecule, glucose, has six carbons, which have been numbered. The sugar to its right is the same glucose, with all but one “C” removed. The other five carbons are still there but are inferred using the conventions of organic chemistry: Anywhere there is a corner, there’s a carbon unless otherwise indicated. It might be a good exercise for you to add in a “C” over each corner so that you gain a good understanding of this convention. You should end up adding in five carbon symbols; the sixth is already given because that is conventionally included when it occurs outside of the ring.

On the left is a glucose with all of its carbons indicated. They’re also numbered, which is important to understand now for information that comes later. On the right is the same molecule, glucose, without the carbons indicated (except for the sixth one). Wherever there is a corner, there is a carbon, unless otherwise indicated (as with the oxygen). On the bottom left is ribose, the sugar found in RNA. The sugar on the bottom right is deoxyribose. Note that at carbon 2 (*), the ribose and deoxyribose differ by a single oxygen.

The lower left sugar in the figure is a ribose. In this depiction, the carbons, except the one outside of the ring, have not been drawn in, and they are not numbered. This is the standard way sugars are presented in texts. Can you tell how many carbons there are in this sugar? Count the corners and don’t forget the one that’s already indicated!

If you said “five,” you are right. Ribose is a pentose (pent = five) and happens to be the sugar present in ribonucleic acid, or RNA. Think to yourself what the sugar might be in deoxyribonucleic acid, or DNA. If you thought, deoxyribose, you’d be right.

The fourth sugar given in the figure is a deoxyribose. In organic chemistry, it’s not enough to know that corners indicate carbons. Each carbon also has a specific number, which becomes important in discussions of nucleic acids. Luckily, we get to keep our carbon counting pretty simple in basic biology. To count carbons, you start with the carbon to the right of the non-carbon corner of the molecule. The deoxyribose or ribose always looks to me like a little cupcake with a cherry on top. The “cherry” is an oxygen. To the right of that oxygen, we start counting carbons, so that corner to the right of the “cherry” is the first carbon. Now, keep counting. Here’s a little test: What is hanging down from carbon 2 of the deoxyribose?

If you said a hydrogen (H), you are right! Now, compare the deoxyribose to the ribose. Do you see the difference in what hangs off of the carbon 2 of each sugar? You’ll see that the carbon 2 of ribose has an –OH, rather than an H. The reason the deoxyribose is called that is because the O on the second carbon of the ribose has been removed, leaving a “deoxyed” ribose. This tiny distinction between the sugars used in DNA and RNA is significant enough in biology that we use it to distinguish the two nucleic acids.

In fact, these subtle differences in sugars mean big differences for many biological molecules. Below, you’ll find a couple of ways that apparently small changes in a sugar molecule can mean big changes in what it does. These little changes make the difference between a delicious sugar cookie and the crunchy exoskeleton of a dung beetle.

Sugar and Fuel

A marathon runner keeps fuel on hand in the form of “carbs,” or sugars. These fuels provide the marathoner’s straining body with the energy it needs to keep the muscles pumping. When we take in sugar like this, it often comes in the form of glucose molecules attached together in a polymer called starch. We are especially equipped to start breaking off individual glucose molecules the minute we start chewing on a starch.

Double X Extra: A monomer is a building block (mono = one) and a polymer is a chain of monomers. With a few dozen monomers or building blocks, we get millions of different polymers. That may sound nutty until you think of the infinity of values that can be built using only the numbers 0 through 9 as building blocks or the intricate programming that is done using only a binary code of zeros and ones in different combinations.

Our bodies then can rapidly take the single molecules, or monomers, into cells and crack open the chemical bonds to transform the energy for use. The bonds of a sugar are packed with chemical energy that we capture to build a different kind of energy-containing molecule that our muscles access easily. Most species rely on this process of capturing energy from sugars and transforming it for specific purposes.

Polysaccharides: Fuel and Form

Plants use the Sun’s energy to make their own glucose, and starch is actually a plant’s way of storing up that sugar. Potatoes, for example, are quite good at packing away tons of glucose molecules and are known to dieticians as a “starchy” vegetable. The glucose molecules in starch are packed fairly closely together. A string of sugar molecules bonded together through dehydration synthesis, as they are in starch, is a polymer called a polysaccharide (poly = many; saccharide = sugar). When the monomers of the polysaccharide are released, as when our bodies break them up, the reaction that releases them is called hydrolysis.

Double X Extra: The specific reaction that hooks one monomer to another in a covalent bond is called dehydration synthesis because in making the bond–synthesizing the larger molecule–a molecule of water is removed (dehydration). The reverse is hydrolysis (hydro = water; lysis = breaking), which breaks the covalent bond by the addition of a molecule of water.

Although plants make their own glucose and animals acquire it by eating the plants, animals can also package away the glucose they eat for later use. Animals, including humans, store glucose in a polysaccharide called glycogen, which is more branched than starch. In us, we build this energy reserve primarily in the liver and access it when our glucose levels drop.

Whether starch or glycogen, the glucose molecules that are stored are bonded together so that all of the molecules are oriented the same way. If you view the sixth carbon of the glucose to be a “carbon flag,” you’ll see in the figure that all of the glucose molecules in starch are oriented with their carbon flags on the upper left.

The orientation of monomers of glucose in polysaccharides can make a big difference in the use of the polymer. The glucoses in the molecule on the top are all oriented “up” and form starch. The glucoses in the molecule on the bottom alternate orientation to form cellulose, which is quite different in its function from starch.

Storing up sugars for fuel and using them as fuel isn’t the end of the uses of sugar. In fact, sugars serve as structural molecules in a huge variety of organisms, including fungi, bacteria, plants, and insects.

The primary structural role of a sugar is as a component of the cell wall, giving the organism support against gravity. In plants, the familiar old glucose molecule serves as one building block of the plant cell wall, but with a catch: The molecules are oriented in an alternating up-down fashion. The resulting structural sugar is called cellulose.

That simple difference in orientation means the difference between a polysaccharide as fuel for us and a polysaccharide as structure. Insects take it step further with the polysaccharide that makes up their exoskeleton, or outer shell. Once again, the building block is glucose, arranged as it is in cellulose, in an alternating conformation. But in insects, each glucose has a little extra added on, a chemical group called an N-acetyl group. This addition of a single functional group alters the use of cellulose and turns it into a structural molecule that gives bugs that special crunchy sound when you accidentally…ahem…step on them.

These variations on the simple theme of a basic carbon-ring-as-building-block occur again and again in biological systems. In addition to serving roles in structure and as fuel, sugars also play a role in function. The attachment of subtly different sugar molecules to a protein or a lipid is one way cells communicate chemically with one another in refined, regulated interactions. It’s as though the cells talk with each other using a specialized, sugar-based vocabulary. Typically, cells display these sugary messages to the outside world, making them available to other cells that can recognize the molecular language.

Lipids: The Fatty Trifecta

Starch makes for good, accessible fuel, something that we immediately attack chemically and break up for quick energy. But fats are energy that we are supposed to bank away for a good long time and break out in times of deprivation. Like sugars, fats serve several purposes, including as a dense source of energy and as a universal structural component of cell membranes everywhere.

Fats: the Good, the Bad, the Neutral

Turn again to a nutrition label, and you’ll see a few references to fats, also known as lipids. (Fats are slightly less confusing that sugars in that they have only two names.) The label may break down fats into categories, including trans fats, saturated fats, unsaturated fats, and cholesterol. You may have learned that trans fats are “bad” and that there is good cholesterol and bad cholesterol, but what does it all mean?

Let’s start with what we mean when we say saturated fat. The question is, saturated with what? There is a specific kind of dietary fat call the triglyceride. As its name implies, it has a structural motif in which something is repeated three times. That something is a chain of carbons and hydrogens, hanging off in triplicate from a head made of glycerol, as the figure shows.  Those three carbon-hydrogen chains, or fatty acids, are the “tri” in a triglyceride. Chains like this can be many carbons long.

Double X Extra: We call a fatty acid a fatty acid because it’s got a carboxylic acid attached to a fatty tail. A triglyceride consists of three of these fatty acids attached to a molecule called glycerol. Our dietary fat primarily consists of these triglycerides.

Triglycerides come in several forms. You may recall that carbon can form several different kinds of bonds, including single bonds, as with hydrogen, and double bonds, as with itself. A chain of carbon and hydrogens can have every single available carbon bond taken by a hydrogen in single covalent bond. This scenario of hydrogen saturation yields a saturated fat. The fat is saturated to its fullest with every covalent bond taken by hydrogens single bonded to the carbons.

Saturated fats have predictable characteristics. They lie flat easily and stick to each other, meaning that at room temperature, they form a dense solid. You will realize this if you find a little bit of fat on you to pinch. Does it feel pretty solid? That’s because animal fat is saturated fat. The fat on a steak is also solid at room temperature, and in fact, it takes a pretty high heat to loosen it up enough to become liquid. Animals are not the only organisms that produce saturated fat–avocados and coconuts also are known for their saturated fat content.

The top graphic above depicts a triglyceride with the glycerol, acid, and three hydrocarbon tails. The tails of this saturated fat, with every possible hydrogen space occupied, lie comparatively flat on one another, and this kind of fat is solid at room temperature. The fat on the bottom, however, is unsaturated, with bends or kinks wherever two carbons have double bonded, booting a couple of hydrogens and making this fat unsaturated, or lacking some hydrogens. Because of the space between the bumps, this fat is probably not solid at room temperature, but liquid.

You can probably now guess what an unsaturated fat is–one that has one or more hydrogens missing. Instead of single bonding with hydrogens at every available space, two or more carbons in an unsaturated fat chain will form a double bond with carbon, leaving no space for a hydrogen. Because some carbons in the chain share two pairs of electrons, they physically draw closer to one another than they do in a single bond. This tighter bonding result in a “kink” in the fatty acid chain.

In a fat with these kinks, the three fatty acids don’t lie as densely packed with each other as they do in a saturated fat. The kinks leave spaces between them. Thus, unsaturated fats are less dense than saturated fats and often will be liquid at room temperature. A good example of a liquid unsaturated fat at room temperature is canola oil.

A few decades ago, food scientists discovered that unsaturated fats could be resaturated or hydrogenated to behave more like saturated fats and have a longer shelf life. The process of hydrogenation–adding in hydrogens–yields trans fat. This kind of processed fat is now frowned upon and is being removed from many foods because of its associations with adverse health effects. If you check a food label and it lists among the ingredients “partially hydrogenated” oils, that can mean that the food contains trans fat.

Double X Extra: A triglyceride can have up to three different fatty acids attached to it. Canola oil, for example, consists primarily of oleic acid, linoleic acid, and linolenic acid, all of which are unsaturated fatty acids with 18 carbons in their chains.

Why do we take in fat anyway? Fat is a necessary nutrient for everything from our nervous systems to our circulatory health. It also, under appropriate conditions, is an excellent way to store up densely packaged energy for the times when stores are running low. We really can’t live very well without it.

Phospholipids: An Abundant Fat

You may have heard that oil and water don’t mix, and indeed, it is something you can observe for yourself. Drop a pat of butter–pure saturated fat–into a bowl of water and watch it just sit there. Even if you try mixing it with a spoon, it will just sit there. Now, drop a spoon of salt into the water and stir it a bit. The salt seems to vanish. You’ve just illustrated the difference between a water-fearing (hydrophobic) and a water-loving (hydrophilic) substance.

Generally speaking, compounds that have an unequal sharing of electrons (like ions or anything with a covalent bond between oxygen and hydrogen or nitrogen and hydrogen) will be hydrophilic. The reason is that a charge or an unequal electron sharing gives the molecule polarity that allows it to interact with water through hydrogen bonds. A fat, however, consists largely of hydrogen and carbon in those long chains. Carbon and hydrogen have roughly equivalent electronegativities, and their electron-sharing relationship is relatively nonpolar. Fat, lacking in polarity, doesn’t interact with water. As the butter demonstrated, it just sits there.

There is one exception to that little maxim about fat and water, and that exception is the phospholipid. This lipid has a special structure that makes it just right for the job it does: forming the membranes of cells. A phospholipid consists of a polar phosphate head–P and O don’t share equally–and a couple of nonpolar hydrocarbon tails, as the figure shows. If you look at the figure, you’ll see that one of the two tails has a little kick in it, thanks to a double bond between the two carbons there.

Phospholipids form a double layer and are the major structural components of cell membranes. Their bend, or kick, in one of the hydrocarbon tails helps ensure fluidity of the cell membrane. The molecules are bipolar, with hydrophilic heads for interacting with the internal and external watery environments of the cell and hydrophobic tails that help cell membranes behave as general security guards.

The kick and the bipolar (hydrophobic and hydrophilic) nature of the phospholipid make it the perfect molecule for building a cell membrane. A cell needs a watery outside to survive. It also needs a watery inside to survive. Thus, it must face the inside and outside worlds with something that interacts well with water. But it also must protect itself against unwanted intruders, providing a barrier that keeps unwanted things out and keeps necessary molecules in.

Phospholipids achieve it all. They assemble into a double layer around a cell but orient to allow interaction with the watery external and internal environments. On the layer facing the inside of the cell, the phospholipids orient their polar, hydrophilic heads to the watery inner environment and their tails away from it. On the layer to the outside of the cell, they do the same.
As the figure shows, the result is a double layer of phospholipids with each layer facing a polar, hydrophilic head to the watery environments. The tails of each layer face one another. They form a hydrophobic, fatty moat around a cell that serves as a general gatekeeper, much in the way that your skin does for you. Charged particles cannot simply slip across this fatty moat because they can’t interact with it. And to keep the fat fluid, one tail of each phospholipid has that little kick, giving the cell membrane a fluid, liquidy flow and keeping it from being solid and unforgiving at temperatures in which cells thrive.

Steroids: Here to Pump You Up?

Our final molecule in the lipid fatty trifecta is cholesterol. As you may have heard, there are a few different kinds of cholesterol, some of which we consider to be “good” and some of which is “bad.” The good cholesterol, high-density lipoprotein, or HDL, in part helps us out because it removes the bad cholesterol, low-density lipoprotein or LDL, from our blood. The presence of LDL is associated with inflammation of the lining of the blood vessels, which can lead to a variety of health problems.

But cholesterol has some other reasons for existing. One of its roles is in the maintenance of cell membrane fluidity. Cholesterol is inserted throughout the lipid bilayer and serves as a block to the fatty tails that might otherwise stick together and become a bit too solid.

Cholesterol’s other starring role as a lipid is as the starting molecule for a class of hormones we called steroids or steroid hormones. With a few snips here and additions there, cholesterol can be changed into the steroid hormones progesterone, testosterone, or estrogen. These molecules look quite similar, but they play very different roles in organisms. Testosterone, for example, generally masculinizes vertebrates (animals with backbones), while progesterone and estrogen play a role in regulating the ovulatory cycle.

Double X Extra: A hormone is a blood-borne signaling molecule. It can be lipid based, like testosterone, or short protein, like insulin.

Proteins

As you progress through learning biology, one thing will become more and more clear: Most cells function primarily as protein factories. It may surprise you to learn that proteins, which we often talk about in terms of food intake, are the fundamental molecule of many of life’s processes. Enzymes, for example, form a single broad category of proteins, but there are millions of them, each one governing a small step in the molecular pathways that are required for living.

Levels of Structure

Amino acids are the building blocks of proteins. A few amino acids strung together is called a peptide, while many many peptides linked together form a polypeptide. When many amino acids strung together interact with each other to form a properly folded molecule, we call that molecule a protein.

For a string of amino acids to ultimately fold up into an active protein, they must first be assembled in the correct order. The code for their assembly lies in the DNA, but once that code has been read and the amino acid chain built, we call that simple, unfolded chain the primary structure of the protein.

This chain can consist of hundreds of amino acids that interact all along the sequence. Some amino acids are hydrophobic and some are hydrophilic. In this context, like interacts best with like, so the hydrophobic amino acids will interact with one another, and the hydrophilic amino acids will interact together. As these contacts occur along the string of molecules, different conformations will arise in different parts of the chain. We call these different conformations along the amino acid chain the protein’s secondary structure.

Once those interactions have occurred, the protein can fold into its final, or tertiary structure and be ready to serve as an active participant in cellular processes. To achieve the tertiary structure, the amino acid chain’s secondary interactions must usually be ongoing, and the pH, temperature, and salt balance must be just right to facilitate the folding. This tertiary folding takes place through interactions of the secondary structures along the different parts of the amino acid chain.

The final product is a properly folded protein. If we could see it with the naked eye, it might look a lot like a wadded up string of pearls, but that “wadded up” look is misleading. Protein folding is a carefully regulated process that is determined at its core by the amino acids in the chain: their hydrophobicity and hydrophilicity and how they interact together.

In many instances, however, a complete protein consists of more than one amino acid chain, and the complete protein has two or more interacting strings of amino acids. A good example is hemoglobin in red blood cells. Its job is to grab oxygen and deliver it to the body’s tissues. A complete hemoglobin protein consists of four separate amino acid chains all properly folded into their tertiary structures and interacting as a single unit. In cases like this involving two or more interacting amino acid chains, we say that the final protein has a quaternary structure. Some proteins can consist of as many as a dozen interacting chains, behaving as a single protein unit.

A Plethora of Purposes

What does a protein do? Let us count the ways. Really, that’s almost impossible because proteins do just about everything. Some of them tag things. Some of them destroy things. Some of them protect. Some mark cells as “self.” Some serve as structural materials, while others are highways or motors. They aid in communication, they operate as signaling molecules, they transfer molecules and cut them up, they interact with each other in complex, interrelated pathways to build things up and break things down. They regulate genes and package DNA, and they regulate and package each other.

As described above, proteins are the final folded arrangement of a string of amino acids. One way we obtain these building blocks for the millions of proteins our bodies make is through our diet. You may hear about foods that are high in protein or people eating high-protein diets to build muscle. When we take in those proteins, we can break them apart and use the amino acids that make them up to build proteins of our own.

Nucleic Acids

How does a cell know which proteins to make? It has a code for building them, one that is especially guarded in a cellular vault in our cells called the nucleus. This code is deoxyribonucleic acid, or DNA. The cell makes a copy of this code and send it out to specialized structures that read it and build proteins based on what they read. As with any code, a typo–a mutation–can result in a message that doesn’t make as much sense. When the code gets changed, sometimes, the protein that the cell builds using that code will be changed, too.

Biohazard!The names associated with nucleic acids can be confusing because they all start with nucle-. It may seem obvious or easy now, but a brain freeze on a test could mix you up. You need to fix in your mind that the shorter term (10 letters, four syllables), nucleotide, refers to the smaller molecule, the three-part building block. The longer term (12 characters, including the space, and five syllables), nucleic acid, which is inherent in the names DNA and RNA, designates the big, long molecule.

DNA vs. RNA: A Matter of Structure

DNA and its nucleic acid cousin, ribonucleic acid, or RNA, are both made of the same kinds of building blocks. These building blocks are called nucleotides. Each nucleotide consists of three parts: a sugar (ribose for RNA and deoxyribose for DNA), a phosphate, and a nitrogenous base. In DNA, every nucleotide has identical sugars and phosphates, and in RNA, the sugar and phosphate are also the same for every nucleotide.

So what’s different? The nitrogenous bases. DNA has a set of four to use as its coding alphabet. These are the purines, adenine and guanine, and the pyrimidines, thymine and cytosine. The nucleotides are abbreviated by their initial letters as A, G, T, and C. From variations in the arrangement and number of these four molecules, all of the diversity of life arises. Just four different types of the nucleotide building blocks, and we have you, bacteria, wombats, and blue whales.

RNA is also basic at its core, consisting of only four different nucleotides. In fact, it uses three of the same nitrogenous bases as DNA–A, G, and C–but it substitutes a base called uracil (U) where DNA uses thymine. Uracil is a pyrimidine.

DNA vs. RNA: Function Wars

An interesting thing about the nitrogenous bases of the nucleotides is that they pair with each other, using hydrogen bonds, in a predictable way. An adenine will almost always bond with a thymine in DNA or a uracil in RNA, and cytosine and guanine will almost always bond with each other. This pairing capacity allows the cell to use a sequence of DNA and build either a new DNA sequence, using the old one as a template, or build an RNA sequence to make a copy of the DNA.

These two different uses of A-T/U and C-G base pairing serve two different purposes. DNA is copied into DNA usually when a cell is preparing to divide and needs two complete sets of DNA for the new cells. DNA is copied into RNA when the cell needs to send the code out of the vault so proteins can be built. The DNA stays safely where it belongs.

RNA is really a nucleic acid jack-of-all-trades. It not only serves as the copy of the DNA but also is the main component of the two types of cellular workers that read that copy and build proteins from it. At one point in this process, the three types of RNA come together in protein assembly to make sure the job is done right.


 By Emily Willingham, DXS managing editor 
This material originally appeared in similar form in Emily Willingham’s Complete Idiot’s Guide to College Biology

Motherhood Defined: It is in the heart of the beholder

“Motherhood”: Sculpture at the Catacumba Park, Rio de Janeiro, Brazil
Motherhood.  It can mean many things, and our own definition of it is largely defined by our individual experiences.  To one person, motherhood might simply mean the act of raising children; to another, motherhood might be what defines them.  

It is not uncommon to generalize the concept of “motherhood” and lump everyone who upholds a single criterion – being a mom – into one group.   But, really, motherhood affects us all in one way or another, and that way is as unique as the pattern of curves and ridges on a fingertip.

Despite the recent outbreak of (heated) discussion surrounding the Time cover story depicting a beautiful and young woman nursing a toddler, and the questioning if following a certain philosophy makes one more or less of a mother, humans, as a whole, are truly bound by a common goal: to raise the next generation to the best of our abilities under the circumstances at hand.   
But, there is no one answer.
Every mom will have her own definition of motherhood.  But, being a mom is by no means a prerequisite for understanding motherhood as it relates to an individual.  For this special Mother’s Day post, we would like to pay homage to motherhood in its many forms.  Here you will not find a singular description of motherhood.  What you will find, however, is what it means on a more personal level, which is to say that the definition can only come from the heart. 

Thank you to all of the wonderful people who participated in this project (and with short notice!) – we have answers in paragraph, tweet, and prose forms.    

Ilina Ewen, Blogger at Dirt and Noise@IlinaP

What does motherhood mean to me?

Motherhood means feeling a kaleidoscope of emotions simultaneously – fear, glee, worry, angst, pride. And it means being an advocate and a revolutionary who empowers her children to engage in society in a meaningful, fun, vibrant way. And lastly, motherhood means always giving up the biggest piece of cake and the last popsicle and being okay with that.

Momma, PhD, Scientist/Wife/Mother

Motherhood means accepting responsibility. If you read the news or listen to the hype, you know what I mean.  Every choice you make, from before a child is conceived, until long after you’re dead, there is someone out there that will tell you how it impacted your kid. As my nana always said, “It’s always the mother’s fault.”  I just hope that as the time passes I get more credit than blame for how my kids turn out.

Motherhood is how you stretch your heart in ways you never thought possible. It’s how you love through the ups & down, the challenges that life brings. And, it lasts a lifetime from that first tiny cry. 

Chris Gunter, Director of Research Affairs, HudsonAlpha Institute for Biotechnology, @Girlscientist

I’m a human geneticist by training, so I’ve been told having a child is the ultimate version of participating in my research. But the science analogy that best summarizes it for me is maternal-fetal microchimerism. Data demonstrating that my son and I each likely have some of each other’s intact cells inside us forever — as I have with my mother, and she with hers, and so on — beautifully represent to me the meaning of motherhood. As the quote from Elizabeth Stone goes, having a child “is to decide forever to have your heart go walking around outside your body.” To me, that includes half my DNA, some of my cells, and so many of my hopes and dreams, all in one sweet, kissable package.

Dr. Cheryl G. Murphy, Optometrist and Science Writer, @MurphyOD

Motherhood: As a mom of triplets, some would say I have triple the work but I like to think of it as triple the hugs, triple the joy, triple the fun! And when people ask me what it’s like to become a mom I tell them “it’s the toughest job you’ll ever love.” Happy Mother’s Day to all of you amazing, do-it-all moms out there! 

Matt Shipman, Science writer, and founder of the First Step Project@Shiplives

I’m a man, so I obviously have no first-hand experience as a mother. That said, I was raised by a (wonderful) single mother, and have had the pleasure of watching my wife be an awesome mom to our three daughters. Those experiences have shaped my impressions of motherhood. To me, motherhood means being kind, but honest. Being gentle, but strong. Being nurturing, but encouraging independence. Motherhood is letting your kids think you are ten feet tall and bulletproof, so they feel you can keep them safe — even though there’s stuff out there that scares the hell out of you. It’s encouraging your kids to learn new things and to work their butts off in school, without making them feel stupid. Motherhood is leading by example when it comes to telling right from wrong, and showing your kids which battles are worth fighting. And, when the time comes, motherhood is letting go of the reins to see where the kids go on their own. Motherhood is not for wimps.

Julie Marsh, VP of Operations, Cool Mom Picks + Cool Mom Tech@coolmompicks@coolmomtech 

To me, motherhood means leading by example in the most pivotal role I’ve ever accepted.

Emily Willingham, PhD, managing editor, Double X Science, science writer and editor, biologist, autism parent, mother, @ejwillingham

The greatest realization of motherhood for me was that the children we have are people of their own, not “our” children or some kind of nutty, messy, screaming, demanding “other” invading our space, disrupting our lives, and taking our precious time. They are people I love to have around me because they make me laugh, they bring out the teacher in me (not hard to do), they are cool and interesting and imaginative and fun, and each of them (I have three) is a complete individual with a unique personality, outlook, potential, talent, and beautiful, beautiful face that I love to see every day. Just as I choose to spend time with others whom I love, respect, admire, and laugh with, I choose to do the same with my children. That said, I also still have what I had before my children arrived–a happy, full busy life with a partner to whom I seem to grow closer every day, and work that I love. Thanks to my children, I’ve got something even more–three more wonderful people added to my life whom I am deeply delighted and, frankly, honored to know. As Bill Murray’s character in Lost in Translation observes, “They learn how to walk and they learn how to talk… and you want to be with them. And they turn out to be the most delightful people you will ever meet in your life.”

Alice Callahan, Science of Mom@Scienceofmom

What does motherhood mean to me?

Motherhood is humbling. Of all the endeavors I have tackled in my life, never have I wanted so badly to get everything right and yet known that I would not. Never have I been so emotionally invested in the results, so exhausted by the labor of it, and also, so strangely confident that it will turn out OK. It is the most human thing I have ever done.

David Wescott, It’s not a Lecture@dwescott1

For men whose ideas of fatherhood were shaped in large part by its absence in our own lives, motherhood may mean something a bit different.  I’m by no means a scholar, but I’ve had the opportunity to speak often and at length with women across the globe on this topic, and to curate their thoughts a bit. These women talk about the feeling of connection to their children they know no one else has.  They describe the magic of watching their little ones narrate the moments of discovery in their lives. They talk about how their children “complete the circle” and teach them the other side of unconditional love. They help you understand why people invoke the lioness or the grizzly when describing the protective instinct.  

My perspective of motherhood is a lot like that last sentiment – it’s the unyielding power that rises up in you when you realize a little person depends on you for everything.  I know that many men step up when left in that situation – I’ve seen it first-hand – but I suspect the feeling is different for women because this little person actually came from you, is an extension of you, is connected to you in ways no man will ever fully understand. 

When I think of motherhood, I think of unconditional love. It’s what my mother gave to me, and it’s what I expect I would feel for the children I don’t intend to have. My mother made countless sacrifices for me, but she was independent and did not allow motherhood to define her. She has always encouraged me to be my own person and chase my own dreams. She didn’t want me to feel constrained by gender roles. I feel fortunate to live in a time when motherhood is a choice, not an obligation. I admire my peers who have chosen to have kids, but I’m content to enjoy the rich mother-daughter relationship I have with my mom without feeling obliged to replicate it. 

Editors note: Christie has recently written a wonderful piece on motherhood at Last Word On Nothing.  Go read it!

Carin Bondar, Blogger and Filmmaker for Scientific American, the David Suzuki Foundation and Huffington Post, @drbondar

As a working mother of 4 very young children, I don’t have much time to reflect on much – this stage of my life is pretty much dedicated to surviving.  I do know that once I decided that I really wanted to start having children (when I was almost finished my PhD) – my life seemed oddly empty.  It was as though I realized that something tremendous was missing and I became completely obsessed with wanting them.  Now that I have them (yes all 4 of them!) there are many times when I feel completely overwhelmed and exhausted, but  I will always remember the feelings of desire to have a family.  I know that my life would be empty and incomplete without my lovely babies.

Jeanne Garbarino, Biology Editor at Double X Science and Rockefeller University Postdoc, @JeanneGarb

For five years, I have been a mother.  I have learned – and am still learning – some very difficult lessons on time management and prioritization, on choosing my battles wisely, and on being ok when things aren’t exactly perfect (or even decent).  But, to be honest, these are all lessons I really needed to have in my life.  Though it might seem a bit counterintuitive, the mostly delightful chaos associated with rearing my girls has given me more focus.  For me, motherhood is more of a state of being, and it has helped me learn how to not sweat the small stuff (for the most part), to be more mindful of the present, and to think more about the future.  Oh, and motherhood also gives me that special golden ticket to buy really cool games and toys (because who isn’t interested in seeing what Doggie Doo is all about), as well as provides a dependable companion for roller coaster rides.

Motherhood had made me stand in my living room as my kids run around me and think how odd it is that I protect these three little persons. Motherhood has made me weep at the sight of children hurt or hungry; has made me rageful at a world where monsters are free; has made me face my own capacity for anger; and it has graced me with random gifts like hysterical laughter over blueberry waffles at the breakfast table. 

Rebecca Guenard, PhD, Atomic-o-licious@BGuenard

Motherhood

Listening to stories,

admiring all they know.

Hugging, kissing,

holding Cheeto-covered hands.

Tightening hockey skates,

washing baseball uniforms.

He stands on the mound alone.

From Twitter

@Scientistmother: motherhood means joyous bittersweet scary make a better person love no matter what

@Cbardmayes: mh=if my heart was as the universe, still would not be big enough to hold all the love for my son & his smiles #happymunkimama

@Labroides:motherhood is seeing my wife find reserves of strength patience and love that we didn’t know she had

@Babyattachmode:to me motherhood means realizing that I have this enormous amount of love for such a little person!

@Jtothehizzoe:The “motherhood” is that end of town where all the moms hang out, actin’ all hard, right?

Organic versus conventional foods–no winner?

A strawberry. Can you tell
if it is organic or not?
[Photo credit:  Rasbak from nl.]
By Emily Willingham

A report on organic foods has just come out from a Stanford University team, and the headlines, such as this one from the New York Times, pretty much say what everyone’s saying about it: Organic foods aren’t any better for you, nutritionally, than conventional foods. 

According to the NYT report, the Stanford researchers spent four years looking over more than 200 studies, evaluating various aspects of research findings about organic versus conventionally farmed or ranched plants and meats. The kind of analysis they did is called a “meta-analysis” because it goes beyond–or “meta”–a single study and looks at a pile of existing data to analyze. 

The NYT piece and a lot of what I’ve been seeing on Twitter gives the impression that people buy organic foods because they think these foods are nutritionally superior to conventionally produced foods. In that context, according to the NYT piece, the researchers

concluded that fruits and vegetables labeled organic were, on average, no more nutritious than their conventional counterparts, which tend to be far less expensive. Nor were they any less likely to be contaminated by dangerous bacteria like E. coli.

The researchers also found no obvious health advantages to organic meats.

The problem? This is purely anecdotal (although at least one poll supports it), but the people I know who buy organic don’t do it because they’ve got some idea that an organic strawberry’s got more vitamin C than a non-organic one. They do it because of the rules governing the production of organic fruits and vegetables and organic meats. Their reasoning is that these processes will result in foods with less pesticide residue and less contamination with antibiotic-resistant bacteria. Guess what the Stanford team found? Again, from the NYT:

Conventional fruits and vegetables did have more pesticide residue, but the levels were almost always under the allowed safety limits, the scientists said

and

Organic produce, as expected, was much less likely to retain traces of pesticides….Organic chicken and pork were less likely to be contaminated by antibiotic-resistant bacteria.

That finding for pesticides alone is one reason many people I know who buy organic do so. 

One of the Stanford researchers acknowledged as much in the NYT piece:

Dr. Bravata agreed that people bought organic food for a variety of reasons – concerns about the effects of pesticides on young children, the environmental impact of large-scale conventional farming and the potential public health threat if antibiotic-resistant bacterial genes jumped to human pathogens. “Those are perfectly valid,” she said.

Indeed, the piece does include an observation from an analyst with the Environmental Working Group noting that the “more nutritious” concept has “never been a major driver” in people’s decision to buy–and pay more for–organic food. That said, organic producers do tend to emphasize the “nutritional superiority” of organically produced foods. Perhaps their advertising is poorly targeted.
Oddly enough, the researchers did find some potentially higher nutritional benefits of some organic foods, such as more “heart-healthy” omega 3 fatty acids in organic milk compared to conventionally produced milk.
What about you? Do you buy organic? If so, what are your reasons? 
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For further reading, check out the online brouhaha that blew up last summer, ignited by this article from Christie Wilcox, writing at Scientific American blogs. 
These views are the opinion of the author and do not necessarily reflect or disagree with those of the DXS editorial team.